Pressurized chambers for controlling deflection of papermaking machine headbox walls

ABSTRACT

A closed, pressure operated, stock inlet box, especially for a papermaking machine, which has walls supporting the lips of the discharge nozzle. The lip supporting walls of the box are constructed as hollow girders and support for the walls is provided by supporting load relief girders adjacent the walls and confining therewith chambers which are pressurized. The load relief girders, according to the invention, are mounted inside the hollow girders of the walls to be supported thereby leading to a compact structure. Mechanical support elements, ribs, for example, disposed between the load relief girders and the supported walls transmit loads from the walls to the load relief girders in the event of loss of pressure in the pressure chambers.

United States Patent [191 Wolf [ Oct. 30, 1973 [75] Inventor: Karl Wolf,

Heidenheim-Schnaitheim, Germany [73] Assignee: J. M. Voith GmbH,Heidenheim (Brenz), Germany [22] Filed: Dec. 2, 1970 [21] Appl. No.:94,517

3,562,106 2/1971 Beck et a1 162/347 X 3,468,756 9/1969 Villa 162/344FOREIGN PATENTS OR APPLICATIONS 1,461,176 10/1969 Germany 162/340Primary Examiner-S. Leon Bashore Assistant Examiner-Richard 1-1. TushinAttorney-Melvin A. Crosby [57] ABSTRACT A closed, pressure operated,stock inlet box, especially for a papermaking machine, which has wallssupporting the lips of the discharge nozzle. The lip [30] ForeignApplication Priority Data supporting walls of the box are constructed ashollow Dec. 13, 1969 Germany P 19 62 634.7 girders and pp for the Wallsis Provided y P- porting load relief girders adjacent the walls and con-[52] us. Cl. 162/340, 162/336, 162/347 fining therewith Chambers whichare pressuriled- The [51] Int. Cl. D211 1/02 load relief girdersaccording to the invention, are 58 Field 6: Search 162/340, 347, 336,mounted inside the hollow girders 0f the walls to be 1 2 339 344supported thereby leading to a compact structure. Me-

chanical support elements, ribs, for example, disposed 56 ReferencesCited between the load relief girders and the supported walls UNITEDSTATES PATENTS transmit loads from the walls to the load relief girdersin the event of loss of pressure in the pressure cham- 3,313,68l 4/1967Dennis et al 162/336 X bets 2,928,464 3/1960 Western et al.... 3,556,9351/1971 Amneus et al 162/347 X 8 Claims, 3 Drawing Figures O 0 I H 2 2239 l PRESSURE l J SUPP]. Y

PATENTEDnm 30 ms INVENTOR. K A QL WO L F PRESSURE U SUPPL r PRESSURIZEDCHAMBERS FOR CONTROLLING DEFLECTION OF PAPERMAKING MACHINE HEADBOX WALLSThe invention relates to a closed and pressure operated stock inlet box,in particular for paper making machines, and having a discharge nozzleextending over the machine width, the nozzle being defined by an upperand lower lip each of which is supported by one wall of the stock inletbox, and each said wall being formed as a hollow girder.

In moderm papermaking machines, which are being constructed withconstantaly increasing operating speeds and machine widths, the walls ofthe stock inlet box of the machine are subjected to ever increasingloadings, namely, and in particular, due to the pressure prevailing inthe interior of the box. The pressure in a stock inlet box increases, asis known, with the velocity with which the stock jet is discharged fromthe said discharge nozzle of the stock inlet box. However, the loadingdue to the dead weight of the stock inlet box is also substantial in thecase of large machine widths. These loadings on the stock inlet boxresult in a corresponding deformation of the walls of the box which, inthe case of lip supporting walls, also effect the lips themselves.

To counteract the effect of wall deflection, a known stock inlet box(German Pat. No. 1,461,176 is provided with a load relief girder on theoutside of each lip supporting wall, constructed as a cavity girder, andbeing adapted to support the respective wall against deflection due tointernal pressure by means of a pressure chamber, extendingsubstantially over the entire machine width and supplied with a pressuremedium. While the above mentioned load relief girder flexes freely dueto the internal pressure transmitted from the pressure chamber, the lipsupporting wall itself is not stressed at all in bending, in the idealcase when the loading is equal on both sides thereof.

However, the ideal case of equal loading on both sides of the lipsupporting wall by no means occurs at all times. For example, it doesnot occur if the pressure in the pressure chamber collapses.Accordingly, even when employing a load relief girder and a pressurechamber, each lip supporting wall must have a substantial sectionmodulus and must be correspondingly dimensioned. To this end, each lipsupporting wall of the above mentioned known stock inlet box isconstructed as a hollow girder the side of which facing the inside ofthe stock inlet box is biased by the internal pressure of the stockinlet box and the side of which facing the exterior bears against thepressure chamber and is biased by the chamber pressure. Accordingly,seen from the side towards the stock inlet box, the cross section ofeach wall has a certain minimum extension. However, the load reliefgirder also has cross-sectional dimensions which are not insubstantial.Accordingly, a structural unit of the kind heretofore described andcomprising a wall and load relief girder occupies a comparatively largeamount of space, which leads to difficulties if the required space isnot available.

With the foregoing in mind, a primary objective of the present inventionis the provision of a stock inlet box of the nature referred to in whichat least one of the walls of the box supporting a lip of the nozzle ofthe box is supported against deflection but without greatly increasingthe cross sectional dimensions of the supported wall.

Another object of the present invention is the provision of a supportingarrangement for a wall of a stock inlet box which supports a lip of thenozzle of the box in which the supporting arrangement is locatedsubstantially completely within the normal cross sectional confines ofthe supported portion of the wall.

Still another object is the provision of a supporting arrangement for awall of a stock inlet box which supports a lip of the nozzle of the boxin which the supporting arrangement employs a pressure medium foreffecting the support but wherein loss of pressure of the medium doesnot result in complete loss of the supporting function of the supportingarrangement.

The foregoing objects as well as still other objects and advantages ofthe present invention will become more apparent upon reference to thefollowing detailed specification taken in connection with theaccompanying drawings, in which:

FIG. 1 shows a stock inlet box for a high speed papermaking machineshown in longitudinal section along the longitudinal axis of themachine.

FIG. 2 is a section taken along the line II--II of FIG. 1 and drawn atenlarged scale and showing a supporting structure comprising hollowgirder, load relief girder and pressure chamber.

FIG. 3 is a fragmentary view like FIG. 2, but shows a modified formwherein the hollow girder is open at the ends.

BRIEF SUMMARY OF THE INVENTION According to the invention the problem issolved in that the load relief girder and the pressure chamberassociated therewith are disposed within the wall which is constructedas hollow girder. The load relief girder is thus completely surroundedby the stock inlet box wall which is constructed as a hollow girder sothat the space requirements of a stock inlet box constructed inaccordance with the invention and, as seen from the side, is no greaterthan that of a conventional stock inlet box which has no load reliefgirder and no pressure chamber.

It is of no consequence whether the hollow girder forming the affectedwall of the stock inlet box is constructed in totally enclosed form orif it has apertures on the end faces and/or on the side opposite to theinterior of the stock inlet box. A hollow girder which is open at theend faces will be used in a preferred embodiment since it is then verysimple to install the load relief girder. The hollow girder forming thewall of the stock inlet box may, however, also be comprises of a plate,facing the interior of the box, and of two stiffening members disposedin longitudinally spaced relation on the exterior of the plate andbetween which the load relief girder is accommodated.

The idea of the invention may be applied to the front wall whichsupports the upper lip of the nozzle as well as to the wall supportingthe lower lip of the nozzle and forming the bottom wall of the stockinlet box. In the first mentioned case, the stock inlet box isshortened, over prior art constructions, in the direction correspondingto the longitudinal machine orientation while, in the other case, acorresponding reduction is obtained in the structural height of thestock inlet box. It is, of course, possible for both the front wall andthe bottom wall of the stock box to be constructed in accordance withthe invention.

The manner in which the load relief girder is mounted in the appropriatehollow wall girder of the respective wall of the stock inlet box is ofno consequence for the method of operation of the entire supportingstructure provided the mounting of the load relief girder is locatedexclusively in the region of the load relief girder ends, in order toensure completely free flexure of said load relief girder. For example,the ends of the load relief girder may be welded directly to the endfaces of the hollow girder, for example to end flanges which are commonto the hollow girder and the load relief girder. However, suchconstruction causes the welding seams to be simultaneously stressed intension and bending and, therefore, result in a relatively unfavorableform of loading. To avoid this unfavorable condition and, in accordancewith a further idea of the invention, it is proposed that the connectionbetween the hollow girder of the wall of the stock inlet box and theload relief girder associated therewith, be provided exclusively by tieelements disposed at the ends of the load relief girder. Such tieelements may, for example, be relatively thin plates which thereforehave flexural elasticity and which do not offer any substantialresistance to the bending moment developed thereon which occurs when theload relief girder is formed. Welded joints, in such an arrangement,are, in practice, stressed only in tension.

In the event that the pressure in the pressure chamber collapses duringoperation of the papermaking machine it is advantageous for spacers tobe disposed within the pressure chamber between the lip supporting wallof the stock inlet box and the load relief girder pertaining thereto,the height of said spacers being preferable identical to the internalwidth of the pressure chamber when the wall of the stock inlet box is inthe unpressurized state on both sides of the wall. Accordingly in thepreviously mentioned emergency, namely, when there is a loss of pressurein the pressure chamber, it is possible for the affected wall of thestock inlet box to bear directly on and be supported by the load reliefgirder. In such a case, the section moduli of the wall of the stockinlet box and of the load relief girder will be additive so that theflexure of the wall of the stock inlet box remains within tolerablelimits.

DETAILED DESCRIPTION The stock inlet box of FIG. I is provided with afront wall I and a bottom wall 2, both constructed in accordance withthe invention, also a stiffened rear wall 3, lateral walls indicated by30, a cover 4, a traversing transmission 5 for the vertical adjustmentof the front wall I, and an inlet chamber 6. A discharge nozzle 20,extending over the entire width of the stock inlet box and having alower lip 21 and an upper lip 22 is formed from the front wall 1 and thebottom wall 2. Perforated rollers 7 and an overflow trough 9 are alsoprovided in the interior of the box.

As can be seen, the front wall 1 is constructed as a hollow girder whichcompletely surrounds a load relief girder 10. A pressure chamber 12,extending over the entire width of the stock inlet box and having aconnection, not shown, for a pressure medium, for example, water isconfined between the said load relief girder 10 and that part of thefront wall 1 which faces the: interior of the stock inlet box. Theinternal pressure in the stock inlet box bears on the internal surfaceof the front wall 1 and is transmitted via the pressure medium in thepressure chamber 12 to the load relief girder 10. The surface offered bythe front wall 1 to the internal pressure is, of course, somewhat largerthan that part of the front wall which is biased by the chamberpressure. However, since the pressure in the pressure chamber 12 can beadjusted to a value exceeding the internal pressure in the stock inletbox, that part of the front wall 1 which faces the interior of the stockinlet box, and therefore the upper lip 22 of the discharge nozzle arepractically free of flexure; only the load relief girder 10 is deformed.

The stock inlet box wall supporting the lower lip 21, namely, the bottomwall 2 is constructed in the same manner as the front wall 1 in the formof hollow girder means. Two hollow girders 30 and 31 of box-shaped crosssection are fixed to the underside of bottom wall 2, each said hollowgirder surrounding one load relief girder 32. A pressure chamber 34 isprovided between each load relief girder and the respective hollowgirder, each chamber being supplied by a pressurized medium from means34a.

As can be seen from FIGS. 2 and 3, the connection between the bottomwall 2, constructed as hollow girder, and the load relief girder 32associated therewith, is formed by two tie elements 36 and 37. These areprovided at both ends of the entire supporting structure and areconstructed as flexurally elastic but inextensible plates. Spacers 38and 39, the height of which is equal to the internal width of thepressure chamber when no pressure is applied to both sides of the bottomare disposed within the pressure chamber 34 on the said bottom wall 2.In the event of loss of pressure in the pressure chamber it is,therefore, possible for the said spacers directly to support the bottomwall 2 on the load relief girder 32. Two of the aforementioned spacers38 extend along the fore and aft edges of each load relief girder,parallel to. the longitudinal extension thereof and also serve for themounting of resilient sealing strips 40 which seal the sides of thepressure chamber 34. The hollow girder forming the front wall 10 isprovided in a like manner with spacers and sealing strips. However,these are not provided with reference symbols in the drawing.

The hollow girder 30 illustrated in FIG. 2 is enclosed all round, thatis to say it is also enclosed at its end faces. By contrast, the hollowgirder 30a, illustrated in FIG. 3, differs therefrom in that its endfaces are constructed in open form in order to simplify the installationof the load relief girder. The pressure chamber disposed between theupper side of the load relief girder 32 in FIG. 3 and the underside ofbottom wall 2 of the stock inlet box is, of course, sealed on all sidesto permit pressure to be developed therein.

Modifications may be made within the scope of the appended claims.

What is claimed is:

1. In a closed and pressure operated stock inlet box, especially for apapermaking machine, and having confining front, rear, and bottom wallsand a laterally extending discharge nozzle, said nozzle comprising upperand lower lips, the upper lip of said nozzle extending from andsupported by said front wall of said stock inlet box, and said lower lipextending from and supported by said bottom wall, hollow girder meansextending transversely of the stock inlet box and connected to said lipsupporting walls on the sides of said walls which face away from saidstock inlet box from imparting stiffness to said lip supporting walls,at least one transversely extending load relief girder means disposedinside a respective hollow girder means and substantially coextensivetherewith in the longitudinal direction, connecting means connectedbetween the periphery of said load relief girder means and therespective said wall and confining a closed pressure chamber between therespective lip supporting wall and the side of the relief girder meansfacing the said wall, said connecting means permitting said reliefgirder means to flex relative to the respective said wall in the regionof said relief girder means between the ends thereof, and means forsupplying a pressure medium to said chamber for supporting therespective wall against deflection due to pressure inside said stockinlet box.

2. A stock inlet box according to claim 1 in which the connection of theends of said load relief girder means to said hollow girder meanscomprises flexible inextensible elements.

3. A stock inlet box according to claim 2 in which said flexibleelements seal said pressure chamber at the ends, and seal members alongthe sides of said chamber which are elongatable so as not to interferewith flexing of the respective said load relief girder means.

4. A stock inlet box according to claim 1 in which said hollow girdermeans are open at at least the ends thereof.

5. A stock inlet box according to claim 1 which includes spacer meansdisposed in said chamber between the respective lip supporting wall andthe side of the load relief girder means facing the wall and free of atleast one thereof and operable for transmitting loads from the said wallto the load relief girder means in the absence of pressure in saidpressure chamber.

6. A stock inlet box according to claim 4 in which said spacer means aredistributed in said pressure chamber and are dimensioned so as to engageboth the said wall and the said load relief girder means when the saidwall is free of pressure on both sides thereof.

7. A stock inlet box according to claim 1 which includes at least onesaid load relief girder means inside the hollow girder means for each ofsaid lip supporting walls of the stock inlet box.

8. A stock inlet box accordng to claim 1 in which the stock inlet boxwall supporting the lower lip of the nozzle forms the lower wall of thestock inlet box, said hollow girder means for said lower wall comprisinga pair of hollow girders spaced longitudinally along the lower wall, anda said load relief girder means inside each said hollow girder of saidlower wall.

1. In a closed and pressure operated stock inlet box, especially for apapermaking machine, and having confining front, rear, and bottom wallsand a laterally extending discharge nozzle, said nozzle comprising upperand lower lips, the upper lip of said nozzle extending from andsupported by said front wall of said stock inlet box, and said lower lipextending from and supported by said bottom wall, hollow girder meansextending transversely of the stock inlet box and connected to said lipsupporting walls on the sides of said walls which face away from saidstock inlet box from imparting stiffness to said lip supporting walls,at least one transversely extending load relief girder means disposedinside a respective hollow girder means and substantially coextensivetherewith in the longitudinal direction, connecting means connectedbetween the periphery of said load relief girder means and therespective said wall and confining a closed pressure chamber between therespective lip supporting wall and the side of the relief girder meansfacing the said wall, said connecting means permitting said reliefgirder means to flex relative to the respective said wall in the regionof said relief girder means between the ends thereof, and means forsupplying a pressure medium to said chamber for supporting therespective wall against deflection due to pressure inside said stockinlet box.
 2. A stock inlet box according to claim 1 in which theconnectioN of the ends of said load relief girder means to said hollowgirder means comprises flexible inextensible elements.
 3. A stock inletbox according to claim 2 in which said flexible elements seal saidpressure chamber at the ends, and seal members along the sides of saidchamber which are elongatable so as not to interfere with flexing of therespective said load relief girder means.
 4. A stock inlet box accordingto claim 1 in which said hollow girder means are open at at least theends thereof.
 5. A stock inlet box according to claim 1 which includesspacer means disposed in said chamber between the respective lipsupporting wall and the side of the load relief girder means facing thewall and free of at least one thereof and operable for transmittingloads from the said wall to the load relief girder means in the absenceof pressure in said pressure chamber.
 6. A stock inlet box according toclaim 4 in which said spacer means are distributed in said pressurechamber and are dimensioned so as to engage both the said wall and thesaid load relief girder means when the said wall is free of pressure onboth sides thereof.
 7. A stock inlet box according to claim 1 whichincludes at least one said load relief girder means inside the hollowgirder means for each of said lip supporting walls of the stock inletbox.
 8. A stock inlet box accordng to claim 1 in which the stock inletbox wall supporting the lower lip of the nozzle forms the lower wall ofthe stock inlet box, said hollow girder means for said lower wallcomprising a pair of hollow girders spaced longitudinally along thelower wall, and a said load relief girder means inside each said hollowgirder of said lower wall.